Originally posted by Bryan:
Well, without having to read through all 42 wonderful pages of information, i was wondering what a good and reliable internet site is for New Zealand weather is? I am traveling over to NZ (Christchurch etc) at the end of next week and am wondering what the weather will be *without coming on here and asking the question straight out :p *

Regards
Bryan

Weather bomb will go down in history
Mar 30, 2007

Northland's wild weather on Thursday is being described as the worst in 150 years.

Records show it was the biggest single rainfall in the region in such a short time.  It experienced a colossal dumping of water in just 36 hours.

The region has been stung by wicked weather many times before, but Thursday's weather bomb will go down in history.

"It was extremely rare," Niwa principle scientist Dr Jim Sallinger says.  "We're looking at the figures now and for a one day event between Mangawai, Whangarei and Kerikeri it looks like at least 125 years, and for the two day event it looks like 150 years."

But it is unlikely to be another 150 years before it returns.

Scientists say the El Nino weather pattern is officially over but La Nina could be here within months and that means winter will be wet.

Sallinger says while La Nina brings cold water to the Pacific Ocean, that causes warmer than normal water temperatures around New Zealand and more northerly and north easterly winds.

He says it could also mean more storms, more often, like the one in the Far North.

"From the phenomena point of view it's very exciting, but then again it causes a lot of damage and sometimes threatens lives, so from that perspective it is very serious and costly."

Photos: Storm\'s severity even more unusual than first thought
12:45PM Friday March 30, 2007

...While based on past-climate data, Northland had suffered a one-in-more-than-100-years deluge, Dr Salinger said: "As the climate warms, this is the sort of thing we expect to see more often."

He added: "As climate warming occurs, the atmosphere can hold more moisture and therefore more rain falls and therefore what we have thought of under past-climate data as one-in-100 or more reduces and might be one-in-50 years or 1-in-20 years."

Originally posted by rainfan:
Wow - thanks for that Nev - didnt even hear that it could be a 1-in-a-150 year event

Originally posted by Nev:

Quote:

Originally posted by rainfan:
[b] Wow - thanks for that Nev - didnt even hear that it could be a 1-in-a-150 year event

Except that we probably don't have reliable records that far back [/b]

Natural Hazards affecting Northland

On 19 and 20 March 1981 the Kerikeri basin catchment was subjected to a rainfall event resulting from intense thunderstorm activity. This event exceeded any other rainfall recorded in New Zealand for an 8.5-hour duration. A maximum rainfall amount of 448mm was recorded in the Kapiro catchment, with a recorded rainfall intensity of 174mm in 2.5 hours.

Whether it is due to global warming or simply the heavy rain phase of cyclic weather patterns, Northland is subject to extremely heavy rainfall events and these appear to be occurring more frequently. Another explanation could well be, and there is some evidence, that extremely high intensity but very localised rainstorms have always been a feature of Northland's climate, and have strongly influenced the landform of parts of the region. Because the heavy rainfall events have tended to hit more remote and less populated areas, few reliable records exist. But it is likely that they occur much more frequently than previously thought.

Flooding from rivers is by far the most widespread and most frequently occurring natural hazard affecting Northland. The upper tributaries of Northland's rivers drop steeply from the region's mountain ranges and hill country. Sediment carried by the rivers has been deposited in the lower valleys, and particularly in the tidal reaches, to create floodplains.

While by their very nature, these floodplains would have been subject to frequent inundation by rivers, clearance of bush from the catchments, changes in the river regimes due to increased sediment loads, and changes in riparian vegetation, have increased the frequency of overflows from the channels.

Flooding of the rivers and floodplains has only become a hazard since humans occupied the flood-prone land and erected structures over and beside the rivers. Similarly, flooding of land adjoining the coast and around tidal estuaries by storm surges and exceptionally high tides has only become a problem since that land has been developed for urban or even farming uses. Most towns in Northland are built partly on floodplains and are subject to flooding.